I followed Dropbox's blog - Fast Document Rectification and Enhancement
To enhancement image, I need solve this formula
J(x,y) = gain(x,y) * I(x,y) + offset(x,y)
Where J is image after enhancement and I is input image. Thank to Royi's answer from this question, i understand how to calculate image J and image I.
How can i calculate gain and offset ?
I tried calculate 2 image I and 2 image J with different size to calculate gain and offset but it still does't work.
Any suggestions would be amazing.